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replace the three ponds which existed in the pre -mining condition. This letter is provided in <br />Attachment 2.05.4(2)(c)-4. The demonstration to allow the permanent retention of Pond 008 is <br />included in Attachment 2.05.3(3)-19. <br />1. Dam Classi kation Criteria <br />The dam classification criteria follow the guidelines of the USDA Soil Conservation Service <br />Technical Release 60 regarding potential for loss of life and damage as a result of dam failure. <br />This classification criterion is shown below. <br />Class A: No realistic threat of damage to property or life in case of dam failure. <br />Class B: Dams located in predominately rural or agricultural areas where failure may damage <br />isolated homes, main highways or minor railroads or cause interruption of use or service of <br />relatively important public utilities. <br />Class C: Dams located where failure may cause loss of life, serious damage to homes, industrial <br />and commercial buildings, important public utilities, main highways, or railroads. <br />Special demonstrations are needed for ponds that have Class B or C dams. However, it is <br />demonstrated below that each of the ponds meets the Class A criteria. <br />Ponds 012 and 013 - As seen on Map 2.05.3(3)-1 Surface Hydrology, Ponds 012 and 013 are <br />located immediately outside the floodplain of Tuttle Draw. Any dam break of these ponds would <br />discharge water directly into Tuttle Draw. There is no chance the water could harm anything or <br />anyone at other locations. There are no structures that could be affected by a small volume in <br />Tuttle Draw since it is large enough to handle substantial peak flows, as shown on Map <br />2.05.3(3)-1. For these reasons, Ponds 012 and 013 are given a Class A designation. <br />Ponds 015, 016, and 018 - Since these ponds are designed to contain the flow from a 100 -year, <br />24-hour event they would only contribute a couple acre-feet to a drainage from overflow or <br />embankment failure. Thus, these ponds are given a Class A designation. <br />Prior to mining at the New Horizon Mine, a small stock pond existed in the pre -mine landscape <br />on the Goforth property. The location of this unnamed pre -mine structure is shown on Map <br />2.04.9-1. A replacement stock pond will be constructed in the postmining surface to provide <br />water for livestock grazing. Applicable design information for the stock pond has been included <br />in Attachment 2.05.3(3)-38. This pond should also have a Class A designation since its relatively <br />small capacity would pose no realistic threat of damage to property or life in case of dam failure. <br />Section 2.05.3(3) Page 14 October 2018 (TR -86) <br />